Just a meat thermometer will work. As for a thermos, tea does not do well in a thermos. As it sits in the thermos, it changes color and taste, making it not so good.
The guide to tea book only tells you how to brew tea western style. Although, you can learn about a few different tea brewing methods here: http://chineseteas101.com/brewingmethod.htm.
Gongfu takes some practice and skill, but can make great tea if done right. The large gaiwan or glass brewing works very well for green and white tea in particular, and also works well for other teas.

You asked for suggestions about the starter samples you ordered:
The Irish Breakfast is smooth and nice to wake up to, while the English Breakfast has a stronger edge that many like. The Earl Grey Bravo was too strong for me but I gave it to a friend who loves it. The Yunnan Gig is good and almost leans toward a green tea taste/texture (to me, anyway).
Of the herbal starter sampler, I've only had the mint and it mixes well with other teas. Since you like lemon (Did you really set a lemon on fire?? LOL!), you'll probably like the citrusy samplers in there.

You might try using some of the blood orange sampler in your chocolate cake creation.

Thermoses work pretty well for keeping your tea hot for a couple of hours, as long as you remove the leaves right after steeping. If you've used it for coffee, though, you may have to work hard at getting out that lingering coffee taste/smell.

If you spend a little time exploring the TeaChat threads, you'll find a ton of info -- and lots of different opinions on how to prepare it. Hope you enjoy your new tea!